Alright, here’s how you force quit an application in the Mac OS without using the apple menu. This is for my own reference and for anyone else who might need it).
1) Go to Macintosh HD > Applications > Utilities> ‘Activity Monitor’.
2.) from the left-most column of ‘Activity Monitor’, get the “Process-ID” of the application you want to quit. Write down the three-digit number.
Note: Every time a process/application runs, the OS assigns it a new Process-ID.
(Above) The Activity Monitor shows a running display so you may need a quick eye to catch your Process-ID. To make it easier you can filter the processes using the “Active Processes” drop-down menu.
4.) Go to Macintosh HD > Applications > ‘Terminal’, and enter “kill [Process-ID]”. The application should quit.